Or so we thought, until it was pointed out by Burrage, Copeland and Hinds that the fields should be observable in vacuum chambers, when measured not with massive probes but with light ones, such as for example single atoms. The idea is that the Chameleon field inside a vacuum chamber would not be suppressed, or not very much suppressed, and then atoms in the chamber are subject to a modified gravitational field, that is the usual gravitational field, plus the extra force from the Chameleon.

You might not believe it, but half a year after they proposed the experiment, it’s been done already, by a group of researchers from Berkeley and the University of Pennsylvania

I am stunned to say the least! I’m used to experiments taking a decade or two from the idea to planning. If they come into existence at all. So how awesome is this?

Here is what they did in the experiment.

They used a vacuum chamber in which there is an atom interferometer for a cloud of about 10 million Cesium atoms. The vacuum chamber also contains a massive sphere. The sphere serves to suppress the field on one arm of the interferometer, so that a phase difference resulting from the Chameleon field should become measurable. The atoms are each brought into superpositions somewhere above the sphere, and split into two wave-packages. They are directed with laser pulses, that make one wave-package go up – away from the sphere – and down again, and the other wave-package go down – towards the sphere – and up again. Then the phase-shift between the different wave-packages is measured. This phase-shift contains information about the gravitational field on each path.

They also make a measurement in which the sphere is moved aside entirely, so as to figure out what is the offset from the gravitational field of the Earth alone, which allows them to extract the (potential) influence of the Chameleon field by itself.

Their data doesn’t contain any evidence for an usual fifth force, so they can exclude the presence of the Chameleon field to some precision which derives from their data. Thanks to using atoms instead of more massive probes, their experiment is the first of which the precision is high enough to rule out part of the parameter space in which a dark energy field could have been found. The models for Chameleon fields have a second parameter, and part of this space isn’t excluded yet. However, if the experiment can be improved by some orders of magnitude, it might be possible to rule it out completely. This would mean then that we could discard of these models entirely.

It is always hard to explain how one can get excited about null results, but see: ruling out certain models frees up mental space for other ideas. Of course the people who have worked on it won’t be happy, but such is science. (Though Justin Khoury, who is originator of the idea, co-authored the paper and so seems content contributing to its demise.) The Chaemeleon isn’t quite dead yet, but I’m happy to report it’s on the way to the nirvana of deceased dark energy models.

For all I know, no, there's no basic motivation for this type of field in particular, unless you want to count the usual 'scalar fields are everywhere and easy to make' argument that is also mentioned in the paper (first paragraph).

"I’m used to experiments taking a decade or two from the idea to planning. If they come into existence at all. So how awesome is this?"

The speed of the experiment is probably because this is a small tweak on experiments they already had going on. Interferometry with cold cesium is what the Muller group does, and adding a sphere in the vacuum chamber is pretty straightforward.

I remember being impressed by two simple things: That try as I could I could not remove all the air out of a bottle, yet with a little force one can open a bellows under water even if its opening is sealed.OK the teachers say nature abhors a vacuum and that little bubble atop the column of mercury when I asked they said there would always be a molecule or two.Even in general science why might a student not think that if you raised a filled hose above 40 feet that the vacuum there might somehow be made to pump water? Later I actually tried it as an experiment which of course I was pretty sure of a null result, but along the way I found a remarkable siphon that allowed me to pour ten thousand candles in ten seconds accurate to the drop.One way to pump water from very deep is to send shock waves thru the column. Anything less depends on how well we can prime the pump or apply ram jets - that is how we teach the young the beginnings of science.

In kind interesting tests are DOI: 10.5281/zenodo.15107 10.5281/zenodo.15439 10.5281/zenodo.15441 10.5281/zenodo.15445 Look. If a postulate could be defended it would not be postulated. Falsify exact vacuum mirror symmetry toward hadrons, then heal physics.

Don't put your pennies on MOND, but do look at page 5 of arxiv.org/abs/0912.2678 where Milgrom refers to the strength of space. Then think back to the balloon analogy for the expanding universe. You have a balloon in a vacuum. The pressure inside is balanced by the tension in the skin, and there's two ways to make it bigger. One way is to increase the pressure, but that's like creating energy ex nihilo. The other way is to reduce the tension of the skin. Make it a bubble-gum balloon. The skin gets thinner and weaker, so it expands, so the skin gets thinner and weaker, and so on.

I agree with you to a point, in that the question as chemistry is trivial, but so trivial nature gives us the evidence for which we still cannot predict with certainty its experiment. The balloon expansion model is rather simplistic, neutrinos cannot spin the other way reaching the speed of light then going beyond it yet they seem to have mass.In the DNA, at T T in a sequence there is new evidence that cyclobutane, four carbons not only can form disrupted by uv but by electrons that are delayed after the exposure thus in the dark.Perhaps it is time we take another look at the foundations of what we mean when we try to resolve the ultraviolet catastrophe.

It what way would such a field rule out a cosmological constant. You still need to describe it and isn't that what the cosmological constant is? Why not try to prove that space/time is stretching i.e. expanding in the lab just like Hubble first discovered at galactic scales and then try to figure out if it's a constant. If it's not a constant then that would be the dark energy wouldn't it?